The emergence of Klebsiella pneumoniae endogenous endophthalmitis in the USA: basic and clinical advances

Endogenous endophthalmitis (EE) is a relatively uncommon but severe infection that comprises 2% to 15% of all cases of endophthalmitis [1-3]. It is commonly associated with underlying immunosuppression including diabetes mellitus, cardiac disease, renal insufficiency and malignancy. While a number of organisms have been implicated in EE, Klebsiella pneumoniae has been recognized as an increasingly prevalent cause of EE in the Asian population [1,2,4-12]. In addition to numerous case series from Asia, a growing body of basic scientific research has begun to elucidate the pathophysiology of this particular infection. In this case series and review, we report two cases of systemic Klebsiella infection that resulted in EE within the USA. We also discuss recent literature that is starting to shed light on the epidemiology and pathophysiology of this condition.The clinical experience with K. pneumoniae endogenous endophthalmitis (KPEE) is varied, and comparison of the numerous retrospective studies is difficult due to differences in the methods and reporting criteria [1]. Nevertheless, several large retrospective studies report a surprisingly high number of cases of KPEE among patients with EE (Table？1). Wong et al. reported a series of 27 patients with bacterial EE from Singapore over a 4-year period [6]. Sixty percent of cases were secondary to K. pneumoniae, and 48% of these had hepatobiliary sources of infection. Chen et al. reported 74 patients with EE from Taiwan over a 10-year period [5]. Sixty-one percent of cases were secondary to K. pneumoniae, and 53% of these cases had liver abscess. Ang et al. reported 113 patients with EE from Singapore over a 21-year period [9]. Sixty-one patients (54%) and 71 eyes had KPEE. These studies demonstrate that among patients with EE in Asia, the prevalence of KPEE is high (54% to 61%; Table？1). In contrast, Jackson et al. reported a series of 21 eyes in 19 patients with EE from England over a 17-year period, and only one case wa